Method for automatically laying up plywood panels

ABSTRACT

A METHOD FOR AUTOMATICALLY LAYING UP PLYWOOD PANELS, PARTICULARLY THREE PLY, IS DESCRIBED IN WHICH THE FRONT AND BACK VENEER SHEETS ARE FED CROSSWISE TO RESPECTIVE PARALLEL VACUUM DRUM ASSEMBLIES THAT ARE ROTATED IN OPPOSITE DIRECTIONS. THE DRUMS BEND THE SHEETS ABOUT THE PERIPHERIES THEREOF AND MOVE THE SHEETS IN A 180* PATH TO CONVERGE BETWEEN THE DRUM ASSEMBLIES. A CORE SHEET IS FED BETWEEN THE DRUM ASSEMBLIES TO INTERPOSE BETWEEN THE FRONT AND   BACK SHEETS. THE FRONT, CORE AND BACK SHEETS ARE FED IN A TIMED RELATION TO ALIGN THE LEADING EDGES OF THE SHEETS AS THEY CONVERGE.

May 30, 1972 H. A. KELLER EI'AL METHOD FOR AUTOMATICALLY LAYING UPPLYWOOD PANELS 4 Sheets-Sheet 1 Filed April 9, 1969 IN VIENTORS. HHPOLDfl- KELLER Pl? TRICK J: YOUNG y 30, 1972 H. A. KELLER ErAL 3,666,592

METHOD FOR AUTOMATICALLY LAYING UP PLYWOOD PANELS Filed April 9, 1969 4Sheets-Sheet 2 HRROLD I). KELLER PflTR/CKJI YOUNG BY ww-P flrrys.

I NVE NTOR.

y 30, 1972 .H. A. KELLER ET AL METHOD FOR AUTOMATICALLY LAYING UPPLYWOOD PANELS -?iled April 9, 1969 4 Sheets-Sheet 3 INVENTORS. HHROLDH. KELLER PfiTR/CK .71 YOUNG wdh lbw flTTys.

y 30, 1972 H. A. KELLER ETAL 3,666,592

METHOD FOR AUTOMATICALLY LAYING UP PLYWOOD PANELS Filed April 9, 1969 4Sheets-Sheet 4 43 4 INVENTORS.

HHROLD R. KELLER um k-W- flrrys.

United States Patent O 3,666,592 METHOD FOR AUTOMATICALLY LAYING UPPLYWOOD PANELS Harold A. Keller and Patrick J. Young, Lewiston, Idaho,assignors to Potlatch Forests, Inc., Lewiston, Idaho Filed Apr. 9, 1969,Ser. No. 814,581 Int. Cl. B27d 1/04 US. Cl. 156-285 4 Claims ABSTRACT OFTHE DISCLOSURE A method for automatically laying up plywood panels,particularly three ply, is described in which the front and back veneersheets are fed crosswise to respective parallel vacuum drum assembliesthat are rotated in opposite directions. The drums bend the sheets aboutthe peripheries thereof and move the sheets in a 180 path to convergebetween the drum assemblies. A core sheet is fed between the drumassemblies to interpose between the front and back sheets. The front,core and back sheets are fed in a timed relation to align the leadingedges of the sheets as they converge.

BACKGROUND OF THE INVENTION This invention relates to methods formanufacturing plywood panels and more particularly to methods forautomatically laying up plywood panels from face veneer and core sheets.

Plywood is generally defined as wood panels made up of an odd number ofveneer sheets glued together in which the grain of each sheet isperpendicular to the adjacent sheets. The most common size of plywoodpanels is 4 x 8 feet. Most frequently the grain of the outside veneersheets generally referred to as the face veneers (front and back), runslengthwise with the grain of the interior sheets, collectively referredto as the core, running alternating grain directions. The sheets of thecore that run am'dthwise are generally referred to as the cross bandsheets. The cross band sheets are frequently made up of a plurality ofsmall pieces four feet in length that are positioned in side by siderelation until a full sheet is constructed. If the cross band sheets areto be handled, the small pieces are frequently held together by string,tape or edge gluing.

Even with the availability of the most modern technology and machineriesknown to the plywood industry, most of the plywood panels, are stillbeing assembled or layed up manually. The cost of the manual layup steprepresents a substantial portion of the final cost of the product. It isdiflicult to maintain uniform results with the manuallayup process. Woodmaterial and glue losses from rejection are not insignificant.

Although many attempts have been made in the plywood industry to developefiicient and reliable methods and equipment for automatically laying upplywood panels, noneseem to have been commercially successful.

One reason for the difiiculty lies in the nature of plywood veneers.Plywood veneers are quite thin and delicate requiring equipment that iscapable of efficiently and rapidly handling veneers without subjectingthe veneers to damage. In one .direction the veneer sheets are flexibleand in theother direction the sheets are quite stiff. It is difiicult torapidly and consistently align the edges of the wood veneers during thelayup process because of the thinness and size of the plywood veneers.Misalignment results in an inferior product with material losses.

One of the principal objects of this invention is to provide a methodfor automatically laying up plywood panels which is reliable, efficientand inexpensive.

An additional object of this invention is to provide 3,666,592 PatentedMay 30, 1972 automatic layup method requiring apparatus that requires aminimum of manufacturing floor space and which is inexpensive tomanufacture, simple to operate, and reliable and efficient inperformance.

A further object of this invention is to utilize the directionalstrength properties of the veneer sheets to minimize the spacerequirements of the automatic layup equipment.

An additional object of this invention is to provide a method that canbe performed by compact automatic layup equipment that is capable ofaccurately laying up the plywood veneer with a minimum of wastematerial.

An additional object of this invention is to provide automatic layupmethod carried out by moving the face sheets crosswise in one directionand the core sheet crosswise in an opposite direction between the facesheets and then bending the face sheets into curved converging paths toplace the face sheets on the core sheet with the leading I BRIEFDESCRIPTION OF THE DRAWINGS A preferred embodiment of this invention isillustrated in the accompanying drawings, in which:

'FIG. 1 is a side elevational view of an apparatus for sequentiallylaying up plywood panels embodying the principle features of thisinvention;

FIG. 2 is a plan view of the automatic layup equipment;

FIG. 3 is a fragmentary enlarged side view of a portion of the layupequipment emphasizing the drive system;

FIG. 4 is a vertical cross sectional view taken along line 44 in FIG. 2showing the initial portion of the layup sequence with the face veneersheets moving in an opposite direction to the core sheet; and

FIG. 5 is a vertical cross sectional view similar to FIG. 4 exceptshowing the convergence of the face and core sheets to form a plywoodpanel.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now in detailto the drawings, there is shown in FIG. 1 an automatic layup apparatusgenerally designated by the arrow 10. The apparatus 10 forms plywoodpanels from face sheets and core sheets. The face sheets are placed onboth sides of the core sheet with glue therebetween to adhere the sheetstogether. For purpose of this description one face sheet will bereferred to as the front veneer sheet FS and the other will be referredto as the back veneer sheet BS. The grain of the face sheets runsparallel with the length. The core sheet CS may be a single cross bandveneer sheet or may be an uneven number of sheets with the outer sheetshaving their grains running crosswise.

The automatic layup apparatus includes a core feeding section 11, a facesheet feeding section 12 and a layup section 13 all mounted on a generalframework 9. The front and back veneer sheets are fed in a substantiallyhorizontal direction indicated by the arrow 14 in vertically spacedsubstantially horizontal planes 15 and '16 respectively. The horizontalplanes 15 and 16 are sufficiently spaced to permit the face sheets to beflexed and moved in tangential curved paths of approximately to anintermediate horizontal plane .18 that is equidistant between horizontalplanes 15 and 16. The core sheets are fed along the intermediatesubstantially horizontal plane in a horizontal direction 17 that isopposite to the direction 14.

At the layup section 13, the face sheets are moved in a curved pathdesignated by the arrows 19 and 20 to converge in the horizontal plane18. The layup section 13 includes horizontal upper drum assembly 22having a plurality of transversely spaced vacuum wheels 23 (FIGS. 2, 4and '5) mounted on a common axle cylinder 23a that rotates about ahorizontal axis 24 which is perpendicular to the horizontal directions.14 and 17. The peripheries of the wheels 23 are approximately tangentto the horizontal planes 15 and 18.

The vacuum section further includes a lower drum assembly 25 having aplurality of spaced vacuum wheels 26 that are mounted on a common axlecylinder 26a that rotates about a horizontal axis 2 7. The axis 27 isvertically aligned and parallel with the axis 24. The peripheries of thewheels 26 are substantially tangent to the planes 16 and .18.

Each of the vacuum wheels 23 and 26 have apertures 28 therein forcommunicating vacuum pressure from the axle cylinders 23a and 26a to theWheel peripheries. A common vacuum duct 31 (FIG. 2) is mounted on theframework 9 in communication with the axle cylinders 23a and 26a toprovide a source of vacuum pressure for the vacuum wheels.

The veneer sheet feeding section 12 includes a front veneer sheetfeeding means 32 that is elevated vertically above a back veneer sheetfeeding means 33 (FIGS. 1, 4 and The sheet feeding means 32 feeds frontveneer sheets FS crosswise to the drum assembly 22 with the grain of thesheets parallel with the drum axis 24. The sheets are fed tangentiallyto the wheels in such a manner that positive control is maintained onthe sheets to assure precise alignment.

The front veneer sheet feeding means 32 includes a horizontal crowderconveyor 34 comprising a plurality of transversely spaced elongatedcontinuous friction belts 35. The front ends of the belts extend intothe spaces between the vacuum wheels 23 to frictionally bias the sheetsforward until the sheets are on the vacuum Wheels 23. The upper flightof the crowder belts support the sheets in the horizontal plane 15. Thefront veneer sheet feeding means 32 further includes an alignmentconveyor 37 parallel with an in between the crowder belts 35. Thealignment conveyor 37 has two endless chains 38 that are driven througha common drive shaft 40 (FIGS. 4 and 5). The chains 38 have lugs 41mounted thereon at evenly spaced intervals with the lugs of each chaintransversely aligned with lugs of the other chain to align the leadingedge of the sheets on the crowder conveyor parallel with the axes 24 and26 of the vacuum drum assemblies.

The crowder conveyor 34 moves at a faster rate than the lugs 41 to pushthe individual sheets crosswise up against the lugs 41 to align theleading edge so that the sheets are moved onto the vacuum wheels 23 withthe grain of the sheets parallel with the axes of the drum assemblies.

The back veneer sheet feeding means 33 has a similar conveyorarrangement having a crowder conveyor 42 with an alignment conveyor 43in between the individual belts of the crowder conveyor for aligning theleading back veneer sheets parallel with the axis of the Wheels 26. Thelower alignment conveyor 43 has endless chains 44 mounted between thealignment conveyor elements with a plurality of lugs 45 mounted thereonat evenly spaced intervals with each lug transversely aligned with a lugof the other chain for aligning the leading edge of the veneer sheets.The endless chains 44 are driven by a common drive shaft 46.

Longitudinal bar guides 50 are mounted on the framework in asubstantially horizontal relationship spaced immediately above thehorizontal planes 15 and 16 for preventing the veneer sheets fromrippling or buckling while the sheets are being conveyed to the layupsection.

A transverse alignment device (FIG. 2) is mounted alongside each of thecrowder conveyors 34 and 42 for transversely centering the sheets on thebelts. Each of the transverse alignment means includes an uprightcontinuous belt 53 that is mounted at an angle to center the sheets onthe conveyors.

The core feeding section :11 includes a vacuum pickup apparatus 54 thatis mounted over a core stack roll case 55. A stack of core sheets ismoved into position on the roll case so that the major dimension of thecore sheets is perpendicular to the direction 17 and the grain of thecore sheets is paralled with the direction 17. The core vacuum pickupapparatus includes elongated vacuum head 56 that includes a vacuumsource for holding the veneer sheets to the bottom of the vacuum hood.An actuator 57 is mounted on the framework 9 for moving one end of thevacuum head down to grasp the top sheet of a stack and then up to removethe sheet from the stack. The vacuum hood 56 has a vacuum duct 58 thatinterconnects the hood with the vacuum source. A plurality of elongatedhorizontal rollers 59 (FIGS. 4 and 5] driven by synchronous motor 59a,are mounted along the bottom of the vacuum hood perpendicular to thehorizontal direction .17 for moving the core sheets crosswise along thebottom of the vacuum hood 56. The rollers 59 move the core sheetparallel with direction 17 and into an elongated horizontal stop 60(FIGS. 4 and 5). The stop 60 is mounted perpendicular to the horizontaldirection 17 for aligning the leading edge of the core sheets. Theelongated stop 60 includes an elongated flange that extends outwardlyfrom a roll 61. To release the stop the roll 61 is rotated to move thestop out of the path of the sheets and to permit the sheet to move to adrive roller 62 (FIGS. 4 and 5). A nip roller 63 is used in conjunctionwith the drive roller to bias the sheet against the drive roller totransmit the rotation of the drive roller to the sheets. The driveroller 62 is driven by aksynchronous motor 64 that is mounted on theframewor From the drive roller 62 core sheets are fed forward through anadhesive applicator or glue spreader 66. The glue spreader 66 includesupper glue rolls 67 and lower glue rolls 68 for applying adhesive orglue to both sides of the core sheet prior to applying the front andback face veneers to the core sheet at a layup section 13. The rolls 67and 68 are driven by a synchronous motor 69 (FIG. 2) The glue spreader66 is mounted on a movable frame 70 (FIG. 1) that moves transversely ontracks 71 for enabling the glue applicator to be readily andconveniently cleaned. The movable frame 70 has a motor 72 for moving theframe transversely back and forth from the operating position to acleaning position.

A series of discs on an elongated shaft 74 (FIGS. 4 and 5) are mountedbetween the glue spreader and drum assemblies with the shaft axisparallel to the drum assembly shaft and the top peripheries of the discsapproximately tangent to the plane 18. This arrangement supports thecore between the spreader rolls and drum assemblies without undulydisturbing the coating of glue. The discs are driven at the sameperipheral speed as the drum assemblies.

Th e drive means for operating the front veneer sheet feeding means 32,the back veneer sheet feeding means 33 and the core stop 60 issynchronized together through a common drive 75 (FIGS. 1, 2 and 3) sothat the sheets converge between the vacuum wheels in the intermediateplane 18 with the leading edge of each of the sheets vertically alignedto provide the resultant plywood panel with a flush side edge. Thecommon drive 75 is driven from a motor 76 (FIG. 3) that is mounted onthe framework. The motor drives a belt 77 that is connected to a pulley78 mounted on a horizontal main drive shaft 80. The belt 77 also drivesa pulley 81 that is connected to a reduction box 82 for driving the discroller 74. A universal coupling 83 interconnects the main drive shaftwith a shaft 84 which extends to an intermittent drive box 85v forsequentially operating the core stop 60 at precise intervals and incoordination with the position and movement of the lugs 41 and 45.

A universal coupling 87 interconnects the other end of the main driveshaft 80 with a T gear box 88. A drive shaft 90 extends upward from oneside of the gear box 88 and a drive shaft 81 extends downward from theother side. The drive shaft 90 extends to a reduction gear box 92 thatin turn drives a sprocket 93. A chain 94 extends from the sprocket 93 toa sprocket 95 for rotating the upper drum assembly '22. The drive shaft90 also operates a reduction gear 96 that is connected to the driveshaft 40 of the upper alignment conveyor 37.

The drive shaft 91 extends to a reduction gear box 101 having an outputsprocket 102 for driving a chain -3. The chain 103 drives a sprocket 104operatively connected to the axle 2612 of the lower drum assembly. Thedrive shaft 91 also operates a reduction gear box 106 that isoperatively connected to the common drive shaft 46 for moving thealignment conveyor 43.

The relative position of the veneers may be adjusted by adjusting thedrive shafts to the gear boxes.

The automatic layup apparatus also includes an outfeed means 111 forreceiving the formed plywood panels from the layup section and conveyingthe panels in the horizontal plane 18 from the automatic layupapparatus. The outfeed means includes a plurality of continuous belts112 that are positioned between the vacuum wheels 26 with the upperflights of the belts extending along the plane 18 tangentially from theperipheries of vacuum wheels 26. The outfeed means include belt tracks1114 for supporting the upper fiight of the belt conveyors 112. Thebelts 112 also serve the purpose of stripping the back veneer sheetsfrom the vacuum wheels 26 in the horizontal plane 18.

Stripping members 116 are mounted on the framework in the spaces 28between the vacuum wheels 23 of the upper drum assembly and adjacent theintermediate horizontal plane 18 for stripping the front veneer sheetsfrom the vacuum drum as the sheets converge in the intermediatehorizontal plane 18.

The upper drum assembly 22 is supported on a pivotal frame 118 (FIGS. 1and 2) mounted on the framework 9. Actuators 120 (FIGS. 1 and 2) aremounted on the frame 110 with connecting arms extending downward to thepivotal frame 118 for partially supporting the upper drum assembly 22 toreduce the pressure on the resultant plywood sheet between the drumassemblies. The position of the actuator 120 may be adjusted byadjustment bolts 121 to increase or decrease the space between thevacuum wheels 23 and 26. Motion equalizing device 123 is operativelyconnected to the connecting arms 122 to equalize the vertical movementat both ends of the drum assembly. The motion equalizing device includea tongue bar 124 rotatably mounted on the frame parallel with the drumaxes. Radius arms 125 extend from the ends of the tongue bar 124 to theconnecting arms 122.

It should be particularly noted that the automatic layup apparatusrequires a minimum of floor space with the veneer face sheets and thecore sheets under positive control during the entire feeding and layupprocess. The front veneer sheet feeding means and the back veneer sheetfeeding means extend between the vacuum wheels so that the positivecontrol of the veneer sheets is maintained while the sheets are beingtransferred to the vacuum drum assemblies. The synchronous drive systemthrough the common drive 75 assures that the leading edge of each of thesheets will be aligned as the sheets converge between the drumassemblies.

What is claimed is:

1. In a method for laying up plywood panels having first and second faceveneer sheets, and an interposed core sheet, the steps comprising:

engaging the leading edge of each first face veneer sheet in asuccessive row of sheets While moving the first face veneer sheets in adirection perpendicular to their wood grain along a first pathcontaining the sheets, the spacing of the engaged leading edges of thesuccessive first face veneer sheets being greater than their sheetdimension perpendicular to the grain;

engaging the leading edge of each second face veneer sheet in asuccessive row of sheets while moving the second face veneer sheets in adirection perpendicular to their wood grain along a second path spacedfrom and underlying the first path, the direction of movement andspacing of the leading edges of the second face veneer sheets beingcommon to that of the first face veneer sheets; releasably engaging theleading edges of individual core sheets along a path containing the coresheets and equally spaced between the first and second paths;

subsequently moving the individual core sheets along the third path in adirection opposite to the direction of movement of the first and secondface veneer sheets along the first and second paths following release ofthe leading edges of the core veneer sheets;

grasping the individual first and second face veneer sheets while theirleading edges are engaged along the first and second paths andsubsequently releasing each sheet from such engagement and impartingmovement to the grasped sheets along converging curved pathsrespectively tangential to the first and third paths and to the secondand third paths while reversing the direction of movement of the sheets;

and synchronously controlling the movement of the grasped leading edgesof the first and second face veneer sheets, the movement of the graspedsheets along the curved paths and the release and movement of the coresheets along the third path to bring individual first and second faceveneer sheets into converging abutting engagement with a core sheetalong the third path with the leading edges of the abutting sheets in acommon plane perpendicular to the third path; and

applying adhesive material to the sheets along one or more of therespective surfaces thereof brought into abutting engagement with oneanother.

2. A method as defined in claim 1 wherein the adhesive material isapplied to both sides of the core sheets prior to interposing the coresheets between the front and back veneer sheets.

3. The method as defined in claim 1 wherein the front and back venoorsheets are moved from the first and second horizontal planes to themid-horizontal planes by synchronized vacuum wheels that are positionedtangentially between the first and second horizontal planes and themid-horizontal plane.

4. The method as defined in claim 3 wherein the front and back veneersheets are stripped from the vacuum wheels at the mid-horizontal plane.

References Cited UNITED STATES PATENTS 1,714,858 5/1929 Elmendorf156-313- 2,318,215 5/1943 Gans 156303 3,384,137 5/1968 Ash 156-3133,438,830 4/ 1969 Harmsworth 156578 3,455,770 7/1969 Dahl, Jr 156-3033,508,993 4/1970 Belcher et al. 156--285 3,133,850 5/1964 Alenius156-458 3,415,707 12/1968 Barnes 156-559 CARL D. QUARFORTH, PrimaryExaminer E. E. IJEHMANN, Assistant Examiner US. Cl. X.R.

